1. Field of the Invention
The present invention is directed generally to a media-sheet post-processing apparatus that performs post-processing on a media sheet delivered thereto and an image forming apparatus that includes the media-sheet post-processing apparatus.
2. Description of the Related Art
In recent years, sheet processing systems that includes a media-sheet post-processing apparatus and an image forming apparatus, such as a copying machine or a printer, that are arranged adjacent to each other so that the media-sheet post-processing apparatus can align the sheets delivered from the image forming apparatus into a set of sheets and then perform stapling and/or hole punching of the sets of sheets have proliferated.
Various techniques for allowing such a media-sheet post-processing apparatus to provide favorable sheet processing have conventionally been devised and employed.
For instance, Japanese Patent Application Laid-open No. 2001-206629 discloses a technique of pinching a set of sheets, in its thickness direction, between rollers provided on a pivotable guide plate, thereby preventing the set of sheets from going out of alignment.
Japanese Patent Application Laid-open No. 2001-302089 discloses a technique of pinching a set of sheets between one of a pair of folding rollers for use in sheet fold and an upstream roller and between the other roller of the folding rollers and a downstream roller to thereby preventing sheets in the set from going out of alignment.
The applicant has proposed a configuration, in an unexamined application (Japanese Patent Application No. 2008-294436), in which after a set of sheets is stacked in a sheet prestack unit, a retaining member is moved to a trailing end portion of the sheets so that the sheets are folded while being pressed by the retaining member.
In the technique described in the unexamined application, when a set of sheets is prestacked in the sheet prestack unit, the retaining member is moved up or down to press the set of sheets at the trailing end portion so that the set of sheets is stacked without fail.
In an attempt of increasing speed at which sheets are processed in an image forming apparatus, intervals between sheets conveyed in the image forming apparatus are generally reduced. However, it is necessary to suspend sheet conveyance during a period of the up or down movement of the retaining member, which has been a bottleneck in speedup of post-processing.